Media processing apparatus, such as document scanners, copiers, printers, fax machines, and other media processing systems that obtains data from, or imprint images and text onto sheet media, include media transport systems to move the sheet media along a transport path. These media transport systems can sometimes jam as the sheet media moves along the media transport path due to problems or abnormalities in either the media processing apparatus or the sheet media itself. Before loading sheet media into the media transport path of a media processing apparatus, an operator typically removes staples, paper clips, or other fasteners used to hold sheet media containing two or more sheets together. However, sometimes the operator fails to remove or even notice these fasteners. Advancing the sheet media along the media transport path without removing the fasteners can cause significant damage to the sheet media, and can also damage the media transport path, imaging or printing system, or other information transfer system located along the media transport path. In addition, removal of the fasteners, particularly staples, can damage the sheet media before the media is loaded, such that two or more sheets remain attached as they are fed into the transport path. If two or more sheets remain attached together with a fastener or as a result of residual damage caused by the removal of the fastener, then the intended processing of the sheet media can be compromised. For example, a failure to independently image the individual sheets in a document scanner can lead to a loss of information.
While systems have been implemented to check for staples, paper clips, or other fasteners binding sheet media together before the sheet media are transported from an input tray into a scanner device, their scope of detection can be limited and they sometimes fail to detect the fasteners binding sheet media transported into the scanner device. In these situations, jams still occur. In addition, these systems often fail to locate the position of a jam within the media transport system.
Some document handler systems detect the presence of staples in documents loaded into an input tray. However, such systems generally only look for staples in predetermined areas of the documents, and are only capable of detecting staples while the documents are in the input tray. Some documents do not fit into the input tray, and thus no staples in these documents would be detected before they are passed into the scanner. Additionally, many types of documents, including those of varying sizes, do not have a “preselected” area for a staple. Thus, the prior systems can miss staples in documents where staples are present but not in the preselected areas that are monitored.
In addition to the problems caused by fasteners, media processing apparatus are particularly prone to problems during the separation of the queued media in the input tray which can also be caused by poor document preparation or stacking, folds or wrinkles in the fed media sheets, different media weights and thicknesses, and other media-related problems, as well as problems with the media transport components themselves, caused by wear, dust and dirt, and other factors. These problems can be particularly acute with high-speed media processing apparatus or with media processing apparatus that handle fragile media. Failure to detect a problem with the handling of the media in time can damage the original media, causing loss of data, require special handling to correct the problem, and reduce equipment efficiency due to down time.
Various approaches have been used for monitoring the transport of sheet media in a media processing apparatus. Automatic media processing systems have used a range of different approaches of mechanical, optical, and audio sensors for the purpose of preventing damage to media being processed.
In one approach, the sound sheet media makes as it moves along media transport path can be used to diagnose the condition of the sheet media. Quiet or uniform sounds can indicate a normal or problem-free passage of the sheet media along the media transport path. Loud, unexpected, or non-uniform sounds can indicate a disruption in the passage of the sheet media such as a stoppage due to jamming or tearing, or physical damage of the sheet media.
Other known methods of detecting jams include using optical or mechanical sensors to monitor the times at which the sheet media passes through various locations along the media transport path. If the sheet media does not arrive at a given location in a given amount of time after the start of transport, a sheet media jam is inferred. These sensors tend to have a limited range of detection, and several sensors are typically required along the media transport path to produce useful results.
Commonly assigned U.S. Pat. No. 8,857,815 describes placing a microphone near the beginning of a sheet media feed path in order to detect the sound of a sheet media jam in progress. The microphone signal is processed by counting the number of sound samples above a given threshold within a sampling window. If the count is sufficiently large, a sheet media jam is signaled. However, information is not provided about the location of the sheet media as it moves along the media transport path. Thus, although sound can be used to detect a jam in progress, information regarding the location of the jam is unavailable.
A need remains for a simple, fast and robust technique to monitor sheet media advanced by media transport systems for various abnormalities. These abnormalities may be caused, for example, by the presence or residual effects of binding objects, or by problems attributable to the presentation or condition of the media itself. There further exists a need for a simple, fast and robust technique to prevent damage to the media, the media transport systems, and the media processing apparatus, to avoid losses of information, and to reduce downtime. In addition, there remains a need for a fast and robust technique to indicate sheet media jams that also accurately identifies the location of the jams along the media transport path.